1. Field of the Invention
This invention relates to an apparatus for separating adjacent rail sections, and more particularly, to an apparatus for electrically insulating a pair of adjacent rail sections that form separate electrical signal system circuits.
2. Description of the Prior Art
It is well known in the art of railroad traffic signaling to electrically insulate adjacent rail sections that form separate electrical signal system circuits. Railroad traffic signals are used to indicate when a particular train may proceed along a section of track or when it is required to stop. The presence or absence of a train at a particular location along a track line actuates railroad signals at other locations along the track line to alert railroad traffic personnel of the exact location of the train. Many railroad signal systems pass current through sections of the track so that each section of the track becomes a part of a separate electrical signal system circuit. As a train passes over a particular section of track, the steel wheels and frame of the train short circuit the section of track to provide a signal to display lights positioned along the track line and to a railroad traffic controller operator's panel. After the train passes a particular section of track, the short circuit is removed from the track section.
Since sections of railroad track are utilized to form a part of the railroad traffic signaling system, it is essential that adjacent track sections be electrically insulated from each other to avoid unintended short circuits that could cause an incorrect signal to be produced. To avoid these unintended short circuits between adjacent rail sections, the adjacent rail sections that form separate electrical signal system circuits are insulated from each other by means of an electrically insulated rail joint.
U.S. Pat. No. 3,100,080 discloses an electrically insulated, bonded rail joint for use between adjacent rail sections. An electrically nonconductive, synthetic thermo-setting resin material is disposed between the splice bars and the adjacent rail sections. The synthetic resin material molecularly engages with the surfaces of the adjacent rail sections and the splice bars to prevent longitudinal movement of the adjacent rail sections relative to each other. The bonding material, having electrically insulating properties, electrically insulates the adjacent rail sections from the splice bars to form an electrically insulated joint. The bonding material provides an electrically insulating rail joint which cannot be loosened when subjected to downward forces applied to the rail joint.
U.S. Pat. No. 3,139,364 discloses an electrically insulating, thermo-setting synthetic bonding resin which is interposed between the otherwise contacting surfaces of the various components of a railway track structure. The bonding resin is applied to the contacting surfaces in liquid form. When cured, the bonding resin forms a molecular bond between the contacting surfaces to electrically insulate the components and seal the contacting surfaces against the ingress of foreign bodies, such as abrasive particles, moisture, or other corrosive materials.
U.S. Pat. No. 3,837,948 discloses a method for forming an adhesively bonded rail joint in which the rail mating surfaces of splice bars connecting adjacent rail ends carry a layer of electrically insulating, non-curing, thermoplastic adhesive. Upon application of moderate heat and pressure, the thermoplastic adhesive conforms in shape to the mating surfaces of the rail ends. Because the thermoplastic adhesive does not cure, the joint bars may be removed from the adjacent rail ends by reheating the adhesive. If desired, the noncuring adhesive may be used in conjunction with an electrically nonconductive cloth material to electrically insulate the splice bars from the adjacent rail ends to form an electrically insulated rail joint.
U.S. Pat. No. 4,466,570 discloses an insulated joint for use between sections of rail that are disposed in adjacent signal circuits. The insulating joint includes a separator disposed between a pair of dielectric end posts. Joint bars connecting adjacent sections of rail are notched to accept a portion of the separator head. The insulating fabric disposed between the joint bar and the rail is also notched at the separator head area to allow the separator head to fit securely into the notched portion of the joint bar.
While it has been suggested by the prior art devices to form an electrically nonconductive rail joint by separating metallic surfaces with an electrically insulating resin bonding material, or to utilize an insulated joint that requires specially constructed components including a separator having an enlarged head portion requiring alterations or modifications to the joint bars and insulating fabric, there is a need for an electrically insulated, mechanically connected and adhesive-bonded joint assembly that can be made from standard railroad operating equipment to simplify insulated joint installation and repair. The cross sectional configuration of the metallic separator utilized in the insulated joint assembly should be substantially identical to the cross-sectional configuration of the adjacent rail sections to be insulated. The mechanical connection and adhesive bonding provides an insulated joint having sufficient strength to withstand forces applied to the joint by temperature induced and other longitudinal stresses, in addition to the stresses applied to the joint by the weight of a passing train.